Understanding the Subscapularis and Its Importance
The subscapularis muscle is a critical part of the rotator cuff, located at the front of the shoulder. Its role is to rotate the arm inward and stabilize the shoulder joint. When this tendon is torn and cannot be repaired due to muscle retraction or degeneration, it can lead to pain, weakness, and shoulder instability. This condition is particularly disabling because the subscapularis is the only muscle providing support at the front of the shoulder.
When Is Pectoralis Major Tendon Transfer Considered?
If the subscapularis tendon is too damaged to repair, surgeons may consider pectoral tendon transfer. In this procedure, part of the pectoralis major (the large chest muscle) is moved from its normal attachment and used to help restore shoulder function. This is often done in younger, more active individuals who are not candidates for joint replacement.
Candidates generally:
- Are under 65 years old
- Have limited arthritis in the shoulder
- Retain strength in other rotator cuff muscles
- Experience pain or instability due to the torn subscapularis
This procedure can also be used in cases where previous subscapularis repairs have failed or in patients who have had shoulder replacements but developed ongoing instability.
Anatomy of the Pectoralis Major
The pectoralis major muscle has two major parts:
- The clavicular head (upper portion)
- The sternal head (lower portion)
These two parts twist as they attach to the front of the upper arm bone (humerus). During surgery, one or both parts may be used for the transfer depending on the technique chosen.
The blood supply and nerve supply to the pectoralis major allow the muscle to be safely divided and moved, especially when care is taken to preserve nearby nerves such as the musculocutaneous nerve, which is at risk during this procedure.
Surgical Technique Overview
There are several ways to perform this transfer:
- Superficial Transfer – The tendon is moved over the nearby conjoined tendon.
- Subcoracoid Transfer – The tendon is passed underneath the conjoined tendon to create a more natural line of pull and avoid compression of other tissues.
Most surgeons prefer a subcoracoid route, especially with transfer of the sternal (lower) part of the pectoralis major. This approach better mimics the native pull of the subscapularis and may improve joint stability.
Our Preferred Approach
- The patient is positioned in a beach-chair sitting posture.
- Through a standard incision at the front of the shoulder, the surgeon carefully separates the deltoid and pectoralis muscles.
- The sternal head of the pectoralis major is released and rerouted beneath the conjoined tendon (a structure made up of two nearby muscles).
- The transferred tendon is then attached to the upper arm bone, typically near the lesser tuberosity (or in some cases the greater tuberosity) using strong sutures or bone anchors.
- Special care is taken to protect nerves and blood vessels in the area.
- A drain is placed to reduce the chance of swelling after surgery.
Recovery After Surgery
After the operation:
- The shoulder is immobilized in a sling for 4–6 weeks.
- Passive motion exercises begin early to prevent stiffness.
- Strength training and active motion are gradually introduced starting at 6–12 weeks.
- Full recovery and improvements in strength can continue for up to a year or more.
Importantly, because the transferred pectoralis muscle works similarly to the subscapularis, no special retraining is needed—your brain quickly learns to use the muscle in its new role.
What to Expect in Terms of Results
In Isolated Subscapularis Tears
Patients with only the subscapularis torn, and no major damage to other rotator cuff muscles, generally have the best outcomes:
- Improved range of motion
- Reduced pain
- Greater ability to perform daily activities
Many regain near-normal shoulder elevation (above 130°) and internal strength, although external rotation may slightly decrease due to the way the transferred muscle is positioned.
In Combined Tears (With Supraspinatus Involvement)
If both the subscapularis and supraspinatus tendons are torn, results depend on whether the supraspinatus is repairable. Patients with repairable supraspinatus tendons do better than those with irreparable tears.
However, most patients still report:
- Less pain
- Improved motion
- Better stability
After Shoulder Replacement (Arthroplasty)
Results are less predictable in patients who had a previous shoulder replacement. While some experience improvement in stability and pain, others may not see significant gains and may require additional surgery.
Long-Term Outcomes – What Happens Over Time?
In a 20-year follow-up study, most patients who underwent pectoralis major transfer continued to report good to excellent outcomes, especially those with isolated subscapularis tears or reparable supraspinatus damage.
Key long-term findings:
- High patient satisfaction
- Low rate of conversion to reverse shoulder replacement (only 1 in 30)
- Mild arthritis developed in some, but it was not typically painful or limiting
- Most patients maintained good shoulder function despite aging
Importantly, complications such as tendon rupture or nerve injury were rare, and even when they occurred, they were often manageable with further treatment.
Summary for Patients
A pectoral tendon transfer is a specialized shoulder surgery used when the subscapularis tendon is beyond repair. It involves moving part of your chest muscle to support the front of the shoulder, helping to restore movement and reduce pain. This surgery can be life-changing, especially for active individuals who are not ready for joint replacement.
You may be a candidate if:
- You are under 65 and active
- You have a torn subscapularis tendon that cannot be fixed
- Your shoulder is painful or unstable
- You have minimal arthritis and functioning remaining rotator cuff muscles
You should know:
- Most patients improve with this surgery
- Full recovery takes time and commitment to therapy
- Long-term satisfaction is high in properly selected patients
